Upper body exercises increase heart rate due to which mechanism?

Upper body exercises increase heart rate due to which mechanism?

• A. The muscles in the upper body that are used push down on the heart
• B. The brain increases heart rate
• C. The lungs expand more
• D. There is no change in heart rate

Answer: (A)

During upper body exercise, contracting upper body muscles act like a pump that pushes blood back toward the heart. This increases venous return, so more blood fills the heart. The heart then responds to this greater filling by increasing its rate to maintain adequate cardiac output for the higher metabolic demand. So the mechanism described—muscles in the upper body pushing blood back toward the heart to boost venous return—best explains why heart rate rises. While brain activity and breathing changes can influence heart rate, they’re not the primary driver of the immediate rate increase during this type of exercise.

During upper body exercise, contracting upper body muscles act like a pump that pushes blood back toward the heart. This increases venous return, so more blood fills the heart. The heart then responds to this greater filling by increasing its rate to maintain adequate cardiac output for the higher metabolic demand. So the mechanism described—muscles in the upper body pushing blood back toward the heart to boost venous return—best explains why heart rate rises. While brain activity and breathing changes can influence heart rate, they’re not the primary driver of the immediate rate increase during this type of exercise.